Conductive film and manufacturing method thereof

Abstract

Disclosed is a high-strength conductive film having excellent conductivity which can be applied in electronic devices, and which further reduces unevenness in conduction. The conductive film comprises modified fine cellulose having at least a carboxyl group and one type or two or more types of conductive substance. Further, the conductive film is formed by a process involving a step for oxidizing cellulose to prepare modified cellulose, a step for making finer the modified cellulose by dispersing the same in a dispersion medium to prepare modified fine cellulose, a step for mixing the modified fine cellulose and the conductive substance to prepare a dispersion liquid, and a step for drying the dispersion liquid to form a conductive film.

The invention claimed is: 
     
       1. A conductive film comprising:
 a cellulose layer comprising a cellulose fiber having at least a carboxyl group in an amount of 1.0 mmol/g to 2.0 mmol/g, said cellulose fiber having a fiber width of 1 nm to 500 nm; and 
 a conductive layer formed on the cellulose layer, the conductive layer consisting of one or more conductive substances. 
 
     
     
       2. The conductive film according to  claim 1 , wherein
 the cellulose is natural cellulose having a cellulose I type crystal structure. 
 
     
     
       3. The conductive film according to  claim 2 , wherein
 the one or more conductive substances includes a conductive polymer. 
 
     
     
       4. The conductive film according to  claim 3 , wherein
 the conductive polymer is one or more selected from the group consisting of polythiophene, polypyrrole and polyaniline. 
 
     
     
       5. The conductive film according to  claim 2 , wherein
 the one or more conductive substances includes fine carbon. 
 
     
     
       6. The conductive film according to  claim 2 , which further contains an ionic liquid. 
     
     
       7. The conductive film according to  claim 2 , wherein a haze value of the conductive film is 30% or less. 
     
     
       8. The conductive film according to  claim 1 , wherein
 the cellulose is modified by using a co-oxidant in the presence of N-oxyl compound. 
 
     
     
       9. The conductive film according to  claim 8 , wherein
 the N-oxyl compound is 2,2,6,6-tetramethylpiperidinooxy (TEMPO). 
 
     
     
       10. The conductive film according to  claim 8 , wherein
 the co-oxidant is hypochlorite. 
 
     
     
       11. The conductive film according to  claim 3 , wherein
 the conductive polymer is one or more selected from the group consisting of polyaniline, polypyrrole, poly thiophene, poly(3-alkylth iophene), poly(dialkylth iophene), poly(para-phenylene), poly(para-phenylene vinylene), polyacetylene, polyphenylene vinylene and poly(3,4-ethylenedioxy)thiophene (PEDOT). 
 
     
     
       12. The conductive film according to  claim 5 , wherein
 the fine carbon is one or more selected from the group consisting of carbon nanotubes, carbon nanofibers, carbon nanoparticles, carbon nanohorns and fullerene. 
 
     
     
       13. A manufacturing method of a conductive film, comprising:
 oxidizing cellulose to form an oxidized cellulose; 
 preparing a liquid dispersion containing oxidized cellulose by dispersing and refining the oxidized cellulose in a dispersion medium to form a modified cellulose fiber having a carboxyl group on a surface thereof; 
 forming a film containing the modified cellulose fiber by drying the liquid dispersion; and 
 forming a conductive film consisting of one or more conductive substances by coating the conductive substances onto the surface of the film containing the modified cellulose fiber. 
 
     
     
       14. The manufacturing method according to  claim 13 , wherein
 the cellulose is oxidized by using a co-oxidant in the presence of N-oxyl compound. 
 
     
     
       15. The manufacturing method according to  claim 14 , wherein
 the N-oxyl compound is 2,2,6,6-tetramethylpiperidinooxy (TEMPO). 
 
     
     
       16. The manufacturing method according to  claim 14 , wherein
 the co-oxidant is hypochlorite. 
 
     
     
       17. The manufacturing method according to  claim 10 , wherein
 the conductive substance is one or more selected from the group consisting of polyaniline, polypyrrole, poly thiophene, poly(3-alkylthiophene), poly(dialkylthiophene), poly(para-phenylene), poly(paraphenylene vinylene), polyacetylene, polyphenylene vinylene and poly(3,4-ethylenedioxy)thiophene (PEDOT). 
 
     
     
       18. The manufacturing method according to  claim 13 , wherein
 the conductive substance is one or more selected from the group consisting of carbon nanotubes, carbon nanofibers, carbon nanoparticles, carbon nanohorns and fullerene.